Expiration core.
Added QuotaBytes to bucket settings struct.
REST api provides safe bucket settings (no passwords).
Don't create default bucket if it's empty name.
Renamed to defaultNumPartitions for naming consistency.
Web UI for bucket quota field at bucket creation.
Use empty string comparison instead of len().
Added BucketSettings.MemoryOnly field.
REST api and web UI for bucket memory only flag.
Check the memoryOnly setting to allow unpersisted buckets.

cbugg: closes bug-400

This still creates a settings.json file and an empty 0-0.store file,
but item mutations won't be persisted.  This should be enough to
unblock breakdancer testing.